The trend of lengthening golf courses to increase their difficulty has resulted in a high percentage of amateur golfers constantly searching for ways to achieve more distance from their golf shots. The golf industry has responded by providing golf clubs specifically designed with distance and accuracy in mind. The size of wood-type golf club heads has generally been increased while multi-material construction and reduced wall thicknesses have been included to provide more mass available for selective placement through the head. The discretionary mass placement has allowed the club to possess a higher moment of inertia (MOI), which translates to a greater ability to resist twisting during off-center ball impacts and less of a distance penalty for those off-center ball impacts.
Various methods are used to selectively locate mass throughout golf club heads, including thickening portions of the body casting itself or strategically adding separate weight element during the manufacture of the club head. An example, shown in U.S. Pat. No. 7,186,190, discloses a golf club head comprising a number of moveable weights attached to the body of the club head. The club head includes a number of threaded ports into which the moveable weights are screwed. Though the mass characteristics of the golf club may be manipulated by rearranging the moveable weights, the cylindrical shape of the weights and the receiving features within the golf club body necessarily moves a significant portion of the mass toward the center of the club head, which may not maximize the peripheral weight of the club head or the MOI.
Alternative approaches for selectively locating mass in a club head utilize composite multi-material structures. These composite structures utilize two, three, or more materials that have different physical properties including different densities. An example of this type of composite club head is shown in U.S. Pat. No. 5,720,674. The club head comprises an arcuate portion of high-density material bonded to a recess in the back-skirt. Because composite materials like those found in the club head must be bonded together, for example by welding, swaging, or using bonding agents such as epoxy, they may be subject to delamination or corrosion over time. This component delamination or corrosion results in decreased performance in the golf club head and can lead to club head failure.
Further alternatives include a weight that is positioned within a channel formed in a golf club head. Generally, the weight must be inserted into an enlarged portion of the channel and then a plug inserted so that the weight is not ejected from the channel during use.
Though many methods of optimizing the mass properties of golf club heads exist, there remains a need in the art for a golf club head comprising at least a removable weight having secure attachment and a low-profile so that the weight does not protrude into the center of the club head and negatively affect the location of the center of gravity.